By using dismantlable adhesion technology, bonded structures maintain the required strength while the products are in use,and can be easily disassembled by applying external stimulation after use, making it possible to recover materials and parts. In this study, we investigated the adhesion properties of dismantlable adhesion materials manufactured by the addition of poly(2-tert-butoxycarbonyloxy)ethyl methacrylate (PBHEMA) containing a BOC group in its side chain to an epoxy adhesive, and the subsequent disassembly behavior was analyzed. Adhesive test specimens were prepared using steel plate cold commercial (SPCC) as the adherend and PBHEMA as the additive using the following two different methods. One method is to directly add PBHEMA and epoxy monolith filler (EM filler) at the same time when mixing the epoxy resin and the amine curing agent (direct mixing method), and another is to fill the voids of the epoxy monolith with PBHEMA in advance, and it is later mixed with an adhesive and cured (filler method). The initial adhesion properties and their change after heating at 200°C for dismantling process were investigated by a lap-shear tensile adhesion test. When PBHEMA was added to the adhesive, the lap-shear tensile adhesive strength decreased as a function of the heating time of the dismantling process. It was confirmed that the BOC group remained unreacted after curing and adhesion at 100°C, and that the BOC group was deprotected after heating at 200°C. We investigated the changes in adhesive strength by changing the formulation, their mixing method, and the dismantling conditions. It was found that a similar dismantling behavior was observed and no significant difference was observed depending on the addition method. The relationships between the glass transition temperatures of the adhesive components, the interaction between the epoxy adhesive and PBHEMA, and the dismantling behavior under various formulation conditions were discussed.

The Tg -disappearing phenomenon in the glass transition region is examined by analyzing viscoelastic properties of highly crosslinked samples of cured epoxy resin. A structure parameter related to the degree of crosslinking of the network structure is derived in a simple statistical mechanical model. Molecular weight of the relaxation element can be estimated from the maximum value of the loss rigidity curve for each relaxation mode by using this model. It is confirmed for epoxy samples that decrease of molecular weight of the linear segment bound with crosslinking units and increase of molecular weight of the relaxation element at the glass transition point are caused with increase of the degree of crosslinking. Tgdisappearing phenomenon is concluded to relate closely with molecular weight difference of relaxation elements for neighboring relaxation processes.

Diluters play crucial role for reducing rotational viscosity of liquid crystal (LC) materials for improvement of response speed of LC displays (LCDs). However, conventional diluters tend to deteriorate relatively easily under ultraviolet (UV) exposure due to existence of vinyl groups. Hence it was difficult to prepare polymer layers in the LC cells by exposing UV for polymerization regarding polymer sustained alignment (PSA) and polyimide-free (PI-free) technologies. In this study, however, we succeeded in development of a highly reliable fluorinated diluter C3-CyFF-Cy-C3 (Cy : cyclohexane group, C3 : propyl group, F : fluorinated group) under the UV exposure, which carries fluorinated groups for inducing stable nematic phase and high affinity with other fluorinated LC compounds. We succeeded in developing the PSA and the PI-free in-plane switching mode LC cells with the diluter developed in this study. The LC cells with the polymer layers formed by the monomer carrying an azobenzene moiety showed both fast response speed and high stability under the UV exposure.

Anthocyanin-stained transparent pH-responsive organic-inorganic polymer hybrids composed of poly(vinyl alcohol)(PVA) and silica gel (SiO2) were synthesized. PVA, tetramethoxysilane (TMOS), and anthocyanin were dissolved in methanol/distilled water (v/v = 1/2) and stirred for 1 h. The solution was placed at 60℃ for 2 weeks, followed by drying under reduced pressure at 60℃ for 48 h to obtain the corresponding organic-inorganic polymer hybrid (PVA/SiO2 = 5/5).The obtained polymer hybrid showed pH responsive color change such as a reddish-purple color at pH 1.97, an orange color at pH 6.74, and a yellow color at pH 12.38 in buffer solutions. The absorbance of the organic-inorganic polymer hybrid film composed of PVA/SiO2 = 9/1 at 522 nm was measured from pH 1.94 to pH 6.01. As a result, the absorbance tended to decrease with increasing pH value. This result suggested the possibility of using the organic-inorganic polymer hybrid film for pH measuring tools.

Using aminophenols as starting materials, we synthesized maleimide resins with a unit structure having both an allyloxy group and a maleimide group on one aromatic ring through a multi-step synthesis process. These maleimide resins have a highly crystalline N-aryl type maleimide structure within the molecule. However, the allyloxy group gives them a low melting point and makes them amorphous, resulting in low melt viscosity, good solubility in solvents, and excellent processability. The glass transition temperature of the cured material exceeded 350℃, and thermogravimetric analysis showed high thermal decomposition resistance, confirming that the material possesses high levels of both physical and chemical heat resistance. During the curing reaction, in addition to the polymerization reaction of the maleimide group, a Claisen rearrangement reaction of the allyloxy group occurs, and it is expected that the reaction product will also react with the maleimide group. It has been suggested that the network structure formed by these reactions contributes to improving the mechanical strength of the cured material.